Tag: Adam Block

Temba, his spiral arms wide

By Phil Plait | September 3, 2012 7:02 am

Lying roughly 50 million light years from Earth is the magnificent spiral galaxy NGC 5033. Although that distance is a soul-crushing 500 quintillion kilometers, it’s actually relatively close by on the cosmic scale. Close enough that a lot of detail can be seen in the galaxy… and it also makes for a stunner of a picture:

[Click to darmokenate.]

This shot was taken by friend-of-the-BA-blog Adam Block using the 0.8 meter Schulman Telescope on Mount Lemmon in Arizona. It’s a whopping 13 hour exposure taken in near-true color.

It’s amazing what you can see in just this picture if you know what to look for. The spiral arms of the galaxy are fairly open, which is common enough, but the outer ones stick out a bit more than you might expect. The nucleus is very small and bright, more so than I’d expect for a typical spiral as well. Both of those things led me to expect this is an active galaxy, and that turns out to be the case.

Every big galaxy – ours included – has a supermassive black hole in the center. The Milky Way’s is 4 million times the mass of our Sun! In some galaxies, like ours, happily, the black hole is just sitting there. But in some there is gas actively falling into the hole. It spirals around and forms a very hot and very large disk, which glows fiercely as the matter is heated to temperatures of millions of degrees. They disk can blast out light from radio waves up to X-rays, and we say that the galaxy is "active".

A quick search of the literature didn’t turn up any measurements for the mass of black hole in NGC 5033, but it does confirm that it’s an active galaxy. Interestingly, the black hole is not located in the exact center of the galaxy! That’s very unusual, and indicates that NGC 5033 recently merged with another galaxy, probably a smaller one. It’s a cannibal! But then, most big galaxies are. It’s how they get big… and you’re living inside a big one, so there you go.

This may explain the wide arms on the galaxy as well; a collision and merger can distort the shape of the galaxy. Also, check out all the pink blobs along the arms: those are sites of furious star formation, the hot energetic massive young stars lighting up the gas around them. That also is common after a big collision.

Finally, one more nifty thing. You can see long ribbons of dark dust festooning the galaxy in the inner region. Dust absorbs light from stars behind it. But see how the dust looks like it’s only on one side of the galaxy, the half in the picture below the center? That’s an illusion, sortof. In reality there’s dust orbiting all around the center. However, there are stars above and below the disk of the galaxy, and the ones between us and the far side fill in the darkness a little bit, so the dust is less apparent. I’ve written about this before, and it does happen in quite a few spirals. Click the links in the Related Posts section below to see more gorgeous galaxies with this feature.

It’s funny how much information you can squeeze from a single picture! You have to be careful and not over-interpret it, and of course a lot of the things I’ve written here wouldn’t have been known without other observations of NGC 5033 using different telescopes and different methods in different types of light.

But even just one picture can tell you a lot. And in my opinion – and I tend to be right about these kinds of things – the wave of beauty that flows over you when looking at this picture is only enhanced by knowing more about the galaxy itself… and is boosted in no small way by the fact that we can know these things.

Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona


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CATEGORIZED UNDER: Astronomy, Pretty pictures

The start of a long, long dance

By Phil Plait | May 11, 2012 6:30 am

A hundred million light years away, two gorgeous spiral galaxies are locked in an embrace that may end with them merging, a dance spread across a hundred thousand light years in space and a hundred million years of time.

[Click to galactinate, and yeah, just do it. The hi-res version is big and lush and lovely indeed.]

This image, taken by frequent BABlog contributor Adam Block, shows this cosmic waltz in lovely detail (another wonderful image is available via the ESO as well [UPDATE: … and from Gemini, with a diagram of the two and a nice explanation]). The two galaxies (NGC 5426 on the left, and NGC 5427 on the right) are just starting this eons-long encounter, but affects are already visible. You can see tendrils of material stretching from NGC 5426 to its companion, drawn out by the force of NGC 5427’s gravitational attraction.

Inside the galaxies, you can easily see the pink glow of gas clouds, disturbed by the interaction, starting to furiously churn out hot young stars. Actually, stars of all masses are born in these clouds, but it’s the rare massive stars that have the most impact. They blast out ultraviolet light which makes the gas glow, and will explode as supernovae, lighting things up even more.

In galactic collisions like this the outcome can be difficult to ascertain. Perhaps they’ll pass this one time and do so with sufficient velocity to make this a one-eon stand, continuing on into the night. Or, if their relative speeds aren’t enough, they’ll pull apart, only to be drawn inexorably together once again. Even then they may pass, but this time in an ever-decreasing arc, until finally they merge into one bigger galaxy. Although this plays out over far too long a timespan to watch in real time, we see so many colliding galaxies that it’s like having snapshots at all different stages of evolution (see Related Posts below for lots of collidey goodness).

The general steps here are known, but the specific outcome of this particular encounter is still to be seen.

And we’ll see something like it up close, if not for quite some time: the Andromeda Galaxy will one day collide with our Milky Way, and when that happens we’ll be able to see what a galactic collision looks like… from the inside. Buy your tickets now. The show begins in just a billion years or two.

Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona


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Desktop Project Part 25: Chaos in a galactic nursery
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CATEGORIZED UNDER: Astronomy, Pretty pictures

Desktop Project Part 25: Chaos in a galactic nursery

By Phil Plait | April 19, 2012 6:30 am

[The Desktop Project is my way of a) forcing me to write something every day by 2) posting a brief article about all the astronomical images I’ve collected on my computer’s desktop. I’m actually getting ahead of the onslaught, so I’m thinking this week may see me catching up!]

M82 is classified as an irregular galaxy — that is, one that has no overall shape, but instead a weird, splotchy configuration. When you see a picture of it, you’ll see why… and Adam Block of the Mt. Lemmon SkyCenter has a great one!

See what I mean? You can see an underlying galaxy there, but all that red stuff certainly makes it look, well, irregular.

… but wait a sec. If you look at just the galaxy (the blue stuff), it bears more than a striking resemblance to a run-of-the-mill — if heavily warped — edge-on spiral galaxy. And all that red stuff appears to be emanating from the center, as if its being blown from the core of the galaxy like a giant wind!

This, it so happens, is exactly what’s going on. And the reason is that M82 is prolifically fecund: it’s undergoing an intense burst of star formation, creating stars at a rate far exceeding that of the Milky Way.

Young stars can be extremely energetic, blowing out tremendous winds of gas. All that red stuff is actually warm hydrogen, blasting away from the center of the galaxy where all that star birth is occurring. In fact, there may be as many as 200 clusters of stars in the core of M82, in total containing tens of millions of stars. That’s a lot of engines to drive out that gas. No wonder astronomers used to think the core of the galaxy was exploding! But now we know it’s the opposite: it’s not the deaths of thousands of stars creating that chaos, it’s the births of millions of them.

So what caused this incredible profusion of new stars? M82 lies close to a bigger spiral galaxy called M81, and there’s some indication they are gravitationally interacting. A near collision between the two some time ago may have stirred up the gas in M82, causing it to drop to the center of the galaxy where it became the raw material to build stars.

You might think a collision between two galaxies would result in nothing but calamity. But again, the opposite is true! In astronomy — in everything, really — you have to be careful about your presuppositions. The Universe doesn’t care very much what you think, and will continue to behave according to the laws of nature. We’re the ones who have to change and adapt to what it’s telling us.

Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona


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CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Adam Block, M82, star birth

Desktop Project Part 15: The expanding Fireworks Nebula

By Phil Plait | April 9, 2012 6:30 am

[In an effort to clean off the gazillion astronomical pictures I’ve been collecting on my computer’s desktop, I’m posting one per day until they’re gone, and my PC heaves a sigh of relief.]

In 1901, an obscure star in the constellation of Perseus suddenly flared into brightness, becoming briefly one of the brightest stars in the sky. Called GK Persei (or Nova Persei 1901), it’s an odd beast. While some stars like this just fade away after such an event, even now, more than a century later, GK Persei still suffers through periodic explosions, emitting vast pulses of energy.

In 1902 it was found to have an expanding cloud of gas around it. Adam Block, of the Mt. Lemmon Observatory, put together a wonderful animation showing that nebula expanding over 17 years, from 1994 to 2011:

You can see why it’s called the Fireworks Nebula!

This type of system is called a cataclysmic variable star. It’s a binary: one of the stars is a white dwarf, an ultra-dense ball of matter that used to be the core of a normal star like the Sun. When that star reached the end of its life, it shed its outer layers, exposing its core to space.
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CATEGORIZED UNDER: Astronomy, Pretty pictures

An enigmatic blue bubble in space

By Phil Plait | March 13, 2012 7:00 am

There is something aesthetically pleasing about symmetry, whether it’s on Earth or as it is in the heavens. That may be one of the reasons I love planetary nebulae, the eerie and beautiful structures created when dying stars cast off their outer layers. They come in many strange shapes, and oddly it’s quite rare to find one that appears perfectly circular.

But they do exist, and one of the best examples I have seen yet is Abell 33, the glowing winds from a star located something like 1500 light years away:

How gorgeous is that? [Click to embiggen.] This image was made by BABlog regular Adam Block, using the 0.8 meter (32") Schulman Telescope at the Mount Lemmon SkyCenter. He combined images through four filters for a total observation of 630 minutes, over ten hours, to make this dream-like shot.

A few things jumped out at me. First, that bright star on the edge of it giving it a diamond-ring look is almost certainly just a chance alignment. It’s probably much closer or farther away than the nebula, and coincidentally lined up. But it’s very pretty!

Second, it looks like the central star may be a binary, two stars orbiting each other. I measured their separation on the image, and assuming the distance to the nebula really is 1500 light years (though that’s fairly uncertain; I was surprised that there aren’t many papers in the literature about this object), those two stars are no closer than about 0.03 light years from each other — about 2000 times the distance of the Earth from the Sun! That’s a long way, though not unheard of in binaries. Still, I can’t rule out a coincidental alignment.

Also, it’s obvious the central star(s) is off-center! That does happen, usually if the star is moving rapidly through space. The wind it expels gets "blown back" by gas in between the stars, like steam coming from an old-time train’s spout as it rolls down the track. If that were the case, though, I’d expect the nebula itself to be compressed along one side, which it isn’t. That’s a bit of a mystery.

Third, of course, is how circular it is. The outer rim is nearly a perfect circle, which is really uncommon! You might think that in space spheres are common (which would then look like circles as seen from the outside; see here for why), but in fact that’s rarely the case for planetary nebulae. Most are oval, or barrel-shaped, or something even weirder. It has to do with the way the dying star blows off winds, streams of subatomic particles from its surface. If a star is just sitting there, or rotating very slowly, then sure, the wind might expand as a sphere.

Apparently, though, for most stars something happens to increase their spin before they become planetary nebulae. One thing that could do it would be planets: big planets orbiting the star close in would get swallowed up as the star expands into a red giant (the first step in becoming a planetary nebula). The planet orbits the star faster than the star itself spins, so the planet acts like an egg beater or a whisk, stirring up the star’s insides, and spinning it up. We know planets are common — it’s possible most stars have them — so this explanation makes a lot of sense.

But if you look more closely at the picture of Abell 33, things get weirder. The rim is circular, sure, but the fog on the inside is not. It has two oval holes in it, slightly off center. Moreover, the two ovals are parallel, slanted a bit at the same angle. I’m pretty sure this is a sign that the nebula itself may be more barrel shaped, and the two dark ovals are the open ends of the barrel structure. It makes me think it’s a lot like NGC 1514 (inset here; click to embiggen), which has a similar structure (and also a binary central star, hmmm). In the infrared, NGC 1514 looks like a space station! I’d dearly love to see a high-res infrared shot of Abell 33. Would it have those weird rings too?

All in all, this is a pretty interesting nebula, and I’m fairly surprised it hasn’t been studied more. There are some unusual things going on here, which would make for a pretty good project for someone, I’d bet. Until then, though, I guess we’ll have to be satisfied with just soaking in the beauty of this enigmatic object.

Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona


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CATEGORIZED UNDER: Astronomy, Pretty pictures, Top Post

A dying star with the wind in its hair

By Phil Plait | February 13, 2012 7:00 am

I’ve been doing this astronomy thing for a while, OK? I’ve seen galaxies, clusters, stars, planets… so many I’ve lost count. So it’s hard to find something I’ve never seen before, or even heard of before. So when astrophotographer Adam Block sent me a note about the nebula Abell 31, my first reaction was, "Say what now?", and then I clicked on the picture, and my second reaction was "What the what?" Then my third reaction was to soak in the beauty of this gorgeous object, and my fourth reaction was to nod my head slowly, thinking, "Ahh, I see what’s going on here."

Let me share:

See what I mean? What a beauty! [Click to ennebulenate.]

This image was taken with the 0.8 meter Schulman Telescope at Mt. Lemmon in Arizona, and is the result of an astonishing 21 hours of exposure time in various filters! Right away, that was a clue as to why I had never heard of this object: it’s incredibly faint. A quick perusal of amateur astronomers’ sites proved that to be correct; not too many have observed this jewel because it’s barely detectable.

Abell 31 is a planetary nebula, a cloud of gas formed when a dying star expels winds of matter. At first the wind is slow, but then as the star continues to expire the velocity increases. The faster wind catches up with and slams into the slower wind, forming fantastic shapes, usually displaying amazing symmetry.

Abell 31 isn’t symmetric though! One side is sharply defined, and the other diffuse, fuzzy. I was pretty sure right away what I was seeing: this nebula is in motion, moving through space, and interacting with the thin material between the stars. A literature search confirmed this suspicion: it’s moving through space at relatively high speed. In this picture, the direction of motion is toward the bottom of the frame, and the gas leaving the star in that direction is compressed. Gas heading the other way is moving downwind, and relatively untouched. Think of it like blowing on a dandelion; the side toward your mouth gets compressed, while the other side stays fuzzy.

The red gas is hydrogen, and the blue is oxygen. Interestingly, oxygen is probably located throughout the entire nebula, but only in the center is it close enough to the central star to get lit up and glow. The star doing all the work here is a white dwarf, basically the core of a normal star like the Sun, but exposed after all the outer layers of the star have been shed to form the nebula.

Abell 31’s white dwarf central star is tiny, only about 4 times bigger than Earth (or about 0.04 times the size of the Sun), but it’s incredibly hot, blazing away at about 85,000° Centigrade (150,000°F)! It has about half the mass of the Sun, meaning it probably started out life as a star with twice the mass of our star or so, and lost the rest as it aged and blew those winds. Judging from how fast those winds are blowing outward, the star probably started dying in earnest about 130,000 years ago, after a billion or more years of normal life. What used to be a star a couple of million kilometers across is now this lovely object nearly ten light years wide — that’s 100 trillion kilometers from end to end!

At its distance from the Earth of 2000 light years that makes it pretty big in the sky, roughly half the size of the full Moon. With its light spread out so much, no wonder it’s faint. Too bad: it’s a fascinating object, worthy of study. And it’s also fantastically beautiful, worthy of wider recognition.

And I’d love to see a set of Hubble observations of this! I studied planetaries for several years, and I still sometimes get the desire to poke and prod them again. I’ll just have to wait, I suppose, and be satisfied with images as lovely as this one.

Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona


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CATEGORIZED UNDER: Astronomy, Pretty pictures, Top Post

The gorgeous birth pangs of young stars

By Phil Plait | December 2, 2011 11:05 am

The Sun is literally a middle-aged star; approaching the midpoint between its birth over 4 billion years ago and its eventual death about 6 billion years from now. But the Sun is one of hundreds of billions of stars in the Milky Way galaxy, and we see them at all different ages, from their spastic births to their (in some cases) hyperspastic deaths. In many cases the way a star dies is foretold by how its born, so the study of star birth is a rich and fascinating field.

It’s also surpassingly beautiful, since stars are formed from the swirling chaos of thick clouds of gas and dust, lit up by the various newborns embedded within. You’ll find no finer example of this than the large nebula called Sharpless 2-239, a sprawling stellar nursery about 500 light years away in the direction of Taurus, and you may find no finer picture of it than this one taken by astronomer Adam Block using the 0.8 meter telescope at the Mt. Lemmon SkyCenter in Arizona:

[Click to ennebulenate, and yes, you want to.]

Isn’t that breathtaking? This image shows a portion of a much larger complex which currently has over a dozen stars forming inside it. Several of the stars you see here are quite young, only a few million years old. Since these are low mass stars like the Sun, and will merrily fuse hydrogen into helium for billions of years, this is like seeing a human baby when it’s less than a month old.

And, like babies will, these stars eject material from both ends: called bipolar outflow, twin beams of material (typically called "jets") are screaming out of these newborns at several hundred kilometers per second in opposite directions. These jets slam into the dense surrounding material, compressing it, heating it up, and causing it to glow. The structure you see fanning out to the lower left is from one of these jets, the one headed more or less toward us. The one moving in the other direction is mostly hidden from our view by the thick dust in the region.

But there’s much much more going on here…

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CATEGORIZED UNDER: Astronomy, Pretty pictures, Top Post
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